There is a clutch apparatus of the prior art having the sealing apparatus of this kind, for example, as shown in FIG. 4.
A clutch apparatus 50 includes inner member 51 which engages an input shaft 52 via a serration 53 and has a plurality of cam surfaces 54 on the outer circumferential surface. A hollow outer member 55 is arranged coaxially with the inner member 51 and has a cylindrical surface 56 formed on an inner circumferential surface. An annular wedge-shaped space is formed by a cam surface 54 of the inner member 51 and a cylindrical surface 56 of the outer member 55. A retainer 57 is arranged within the wedge-shaped cylinder in which a plurality of rollers 58, as engaging elements, are held by pockets formed therein. The retainer 57 and thus the rollers 58 are normally urged by a switch spring 59 toward a neutral position. In the neutral position, the rollers 58 do not engage with the cylindrical surface 56 and the cam surface 54. By changing the phase of the retainer, the rollers are moved toward either an engaging position or a disengaging position of the inner member 51 and the outer member 55. Thus the function of the clutch can be achieved.
A rotor 60 having a substantially annular recessed cross-section is secured to the outer member 55 and an armature 61 is arranged opposed to the rotor 60 via a suitable gap therebetween. The rotor 60 and the armature 61 are intimately pressed against each other by energizing an electromagnetic coil 62.
In this clutch apparatus 50, the retainer 57 and the rollers 58 are urged toward the neutral position of the cam surface 54 formed on the inner member 51 by the switch spring 59 when the electromagnetic coil 62 is deenergized. Thus, the inner member 51 and the outer member 55 are kept in the freely rotatable condition with each other. On the contrary, if it is desired that the inner member 51 and the outer member 55 are to be drivingly engaged with each other, the electromagnetic coil 62 is energized in order to intimately attract the armature 61 to the rotor 60 secured to the outer member 55. The frictional torque thus caused by the pressure contact of the armature 61 against the rotor 60 is transmitted to the retainer 57 and the outer member 55 via armature 61 and the rotor 60. This causes a relative rotation between the inner member 51 and the outer member 55. The frictional torque overcomes the force of the switch spring 59 and thus the retainer 57 and the rollers 58 are rotated in the same direction as that of the outer member 55. Accordingly the rollers 58 are moved from the neutral position to the wedge engagement position and thus the inner member 51 and the outer member 55 are drivingly engaged.
The outer member 55 is supported by a housing 64 via a roller bearing 63. Immigration of muddy slurry or foreign matter into the clutch apparatus 50 is prevented by sealing apparatus 65 and 66 arranged at opposite ends of the housing 64.
The sealing apparatus 65, arranged at an externally opened side of the housing 64, is formed by a combination of a slinger and a seal lip which has a superior sealing performance. As shown in FIG. 5, the seal apparatus 65 includes a sealing member 67, and a slinger 68 to be fitted in the outer member 55 as a member of rotational side. The sealing member 67 includes a core member 67a of a substantially L-shaped cross-section and a sealing element 67b adhered to the core member 67a by vulcanization and adapted to be slidably contacted with the slinger 68.
The core member 67a has a cylindrical portion 67aa to be fitted in the housing 64 and an upstanding portion 67ab radially extending from one end of the cylindrical portion 67aa. Similarly, the slinger 68 is also of a substantially L-shaped cross-section and has a cylindrical portion 68a to be fitted on the outer member 55 and an upstanding portion 68b radially extending from one end of the cylindrical portion 68a. The sealing element 67b has one or more side lips 67ba adapted to be slidably contacted with the upstanding portion 68a of the slinger 68 and one or more radial lips 67bb adapted to be slidably contacted with the cylindrical portion 68a of the slinger 68.
In the sealing apparatus 65 of the prior art, since the cylindrical portions 67aa and 68a of the sealing member 67 and the slinger 68 have a high rigidity, the deformation of the cylindrical portions 67aa and 68a caused during the press fitting of them tend to cause deformations of the upstanding portions 67ab and 68b. Thus it is necessary to strictly control the press fit interference. The higher the cross-section of the sealing apparatus 65, the larger the deformation of the upstanding portion 67ab and 68b. Change of the lip interference and/or the warp caused in the upstanding portions often cause the reduction of the sealing performance.
Although it is possible to reduce the amount of press fitting in order to suppress the deformations during the press fitting operation, the reduction of the amount of press fitting would cause the sealing performance of the cylindrical portions 67aa and 68a. 